Blade tilting mechanism for power trowel



.Nov. 11, 1969 P. REBECHINI 3,477,353

F BLADE TILTING MECHANISM FOR POWER 'IROWEL Filed Feb. 5, 1968- 2 Sheets-Sheet l INVENTOR PETER G. REBECHINI 4 ATT'YS.

' Nov. 11, 1969 P. G. REBECHINI BLADE TILTIN'G MECHANISM FOR POWER TROWEL Filed Feb. 5, 1968 2 Sheets-Sheet 2 INVENT OR PETER G. REBECHINI BY/QW'J W Z WM Q- F 3 ATT'YS.

United States Patent US. CI. 94-45 3 Claims ABSTRACT OF THE DISCLOSURE Each of the tiltably mounted blades of the power trowel includes a cam following arm engaged by a common cam collar encircling the downwardly depending shaft which rotates the blades upon operation of the trowels internal combustion engine. An arm is pivotly mounted intermediate the ends thereof from the housing or base of the trowel. One end of this arm engages an upper surface of the collar; the other end thereof is engaged by actuating screw member of a reversible electric motor which is supported from the handle of the trowel. Energizing of this motor in one direction serves to move the collar downwardly relative to the driving shaft thereby simultaneously tilting all the blades in one direction. Operation of the motor in the other direction allows the collar to move upwardly relative to the shaft. The cam following arms follow the collar during the upward movement allowing the blades to tilt in the other direction. The electric motor is energized from a generator mounted adjacent the internal combustion engine and driven thereby. Operator control means are mounted on the handle adjacent the operators hand pieces thereby providing means for selectively energizing the motor in either direction thereof.

Objects of the invention A primary object of the present invention is the provision of new and improved means for changing the angle of tilt or pitch of the blades of a power trowel. Another object of the present invention is the provision of power operated means permitting the operator of the power trowel to change the blade pitch in an easy and almost eflortless manner.

Still another object of the present invention is the provisions of powered means for changing the blade pitch in a power trowel, which means include an electric motor energized by a generator, the latter being mounted on the trowel adjacent the internal combustion engine and driven by the latter.

These and other objects and advantages of the invention will become apparent from the following specification disclosing a preferred embodiment shown in the accompanying drawings.

Description of the drawings FIG. 1 is a perspective view of a power trowel embodying the present invention;

FIG. 2 is an enlarged, fragmentary, side elevational view showing the electrically operated means for changing the pitch of the blades of the power trowel; and

FIG. 3 is a diagram of the circuit used in the embodiment of the invention shown for purposes of illustration.

Description of a preferred embodiment The power trowel includes an internal combustion engine having the usual gasoline tank 11 associated therewith. The engine is mounted on top of a gear box 14. A shaft 15 extends downwardly from this gear box. This shaft mounts a hub 16 at the lower end thereof, which hub pivotally mounts four rods 18 each mounting a blade 20. It will be understood that the blades '20 are driven ice in a circular path by rotation of the shaft 15 which is driven through the gear box 14 from the internal combustion engine 10. It will also be understood that each blade 20 is mounted for pivoting or tilting movement about its associated rod 18 thereby to change the pitch of the blades.

The gear box 14- mounts a plurality of brace arms 22 which in turn mount a blade guard 24 in the form of a circular band. Gear box 14 also mounts a subframe 24 supporting one end of a handle 25 having a pair of handdrips 26 at the other end thereof.

The present invention has to do with power operated means whereby the operator of the power trowel can readily change the pitch of the blades 20. To this end, a collar 28 is mounted on the shaft 15 for rotation therewith but for movement axially thereof. The collar 28 mounts a cam collar plate 29 for movement with the collar. Each rod 18 has a cam following arm 30 extending therefrom in a plane perpendicular to the axis of tilt of the rod 18. Each arm 30 mounts an adjustable cam following bolt 32 which engages the underside of the cam collar 29.

The bracket 24 includes an integral, downwardly extending ear portion 24a which is bifurcated and which carries a pin 34 pivotally mounting an arm 35 intermediate the ends of the latter. One end of this arm carries a roller 36 which engages the upper surface of the cam collar 29. The other end of the arm 35 pivotally mounts a trunnion 38 having a threaded bore which is threadingly engaged with the actuating arm 39 of a reversible electric motor 40. This motor is pivotally mounted on a pin 42, the latter being mounted from a bracket 43 secured to the handle 25.

With reference to FIG. 2, it should be apparent that when the arm 35 is pivoted in a counterclockwise direction upon energizing the motor in the appropriate direction, the cam collar 29 will be forced downwardly thereby simultaneously pivoting all the blades 20 in one direction due to the engagement between the cam following bolt heads 32 and the underside of the collar 29. The aforesaid movement of the arm 35 will serve to tilt the blade 20 shown in FIG. 2 in a clockwise direction and returned to the flat or neutral position shown in solid lines by energizing the motor 40 in the other direction. Upon such energization of the motor, the :arm 35 will be rotated in a clockwise direction for raising the roller 36. During this movement of the roller 36, it will be apparent that the weight of the power trowel will cause the blade 20 to tilt in a counterclockwise direction as the associated bolt head 32 follows upward movement of the collar 29 which in turn follows upward movement of the roller 36. It will be understood that the just described operation of the blade 20 shown in FIG. 2 is typical of the other three blades of the power trowel.

The internal combustion engine 10 drives a pulley 45. A pulley 46 is mounted on a shaft 47 which extends into the gear box for driving the main shaft 15. A belt 48 is trained around the pulleys and 46 thereby allowing the former to drive the latter. The engine 10 of the power trowel mounts a DC. generator 50 which is driven from a pulley 51. The pulley 45 is of the double type and has a belt 52 trained therearound, such belt also being trained around the pulley 51. It should be apparent the internal combustion engine 10 serves to drive the generator 50.

The upper end of the handle 25 mounts a small control panel 55 which includes UP and DOWN buttons (not shown). As will be explained hereinbelow, actuation of such buttons causes selective energizing of the motor 40 in either direction of rotation thereof for controlling the pitch or tilt of the blades 20.

Gear box 14 carries a bracket 57 which mounts an UP limit switch 58 and a DOWN limit switch 59. The limit switch 58 has a movably mounted stem 60 which is arranged to be engaged by the collar 29 to establish the uppermost limit of movement of the latter. The end of the arm 35 adjacent the roller 36 mounts a catch 61 arranged to engage a hook portion (not shown) on the stem 62 of the limit switch 59 thereby to establish the limit of downward movement of the cam collar 29.

The electric circuit for the powered blade tilting mechanism of the present invention is shown in FIG. 3. When the UP button on the panel 55 is depressed, movable contacts 65 will be moved to the position shown in solid lines thereby to energize the armature 66 and field winding 67 of the motor 40 in a direction for tilting the blade 20 (FIG. 2) in a clockwise direction. When the DOWN button is pushed, the movable contacts 65 will occupy the broken line position whereupon the armature and field windings of the motor 40 are energized in the pposite direction for reversing the direction of rotation of the motor thereby to tilt the aforesaid blade 20 in the other direction.

While the invention has been shown in but one form, it will be obvious to those skilled in the art it is not to be so limited. On the contrary, the invention is susceptible of many forms and modifications without departing from the spirit and scope of the appended claims.

I claim:

1. In a power trowel of the type including a plurality of radially extending blades and internal combustion motor means for rotating such blades in a circular path, which trowel includes an operator handle for manual guiding thereof, the improvement comprising, means mounting each of said blades for tilting movement about an axis defining a radius of the circular path of movement of the blades, mechanical actuating means including a member engaged with said blades for simultaneously tilting the latter upon movement of the former thereby to change the pitch of such blades, operating means engaged with such member and including an electric motor motor for moving the former, a generator carried by said trowel and electrically connected with said motor for energizing the latter, said generator being driven by said motor which rotates said blades, and operator control means mounted on said handle for controlling energization of said motor.

2. In a power trowel of the type including an internal combustion engine which drives a depending shaft for rotation about a vertical axis, a plurality of radially extending blades connected to said shaft for being driven thereby in a circular path contained in a plane perpendicular to said axis, which trowel includes a handle for manual guiding thereof, the improvement comprising, each of said blades being mounted from said shaft for tilting movement about a radius of the circular path of movement of such blades, a cam following arm mounted on each blade and extending away from the axis of tilt thereof, a cam collar encircling said shaft and engaged on the underside thereof with each of said arms whereupon the latter follow said collar during upward movement thereof relative to the shaft resulting in simultaneous tilting of the blades in one direction, electrically actuated operating means engage with said collar and including a reversible electric motor arranged to be energized in one direction for forcing the collar downwardly relative to the shaft thereby to tilt the blades in the other direction, said operating means allowing said collar to move upwardly relative to the shaft upon energizing said motor in the other direction thereby to cause tilting of the blades in said one direction, a generator mounted on said trowel, which generator is driven by said engine and is electrically connected with said motor for energizing the same, and electric control means on said handle and connected to said motor for selectively energizing the latter in both directions thereof.

3. The improvement according to claim 2 further defined by, said collar being mounted for rotation in a circular path with said blades, said electrically actuated operating means including a pivotally mounted arm having a roller on one end thereof engaging the upper surface of said collar for controlling up and down movement of the latter during rotation thereof with said blades.

References Cited UNITED STATES PATENTS JACOB L. NACKENOFF, Primary Examiner 

